Conduit fittings which comprise a housing and a mechanism therein, as for instance comprising a pulley box or a valve box, are well known in the arts.
For instance, the U.S. patents to Caracristi, No. 1,627,076, issued May 3, 1927, and to Preston, No. 3,042,378, issued July 3, 1962, each disclose a split type pulley box housing wherein the pulley shaft comprises the bolt that locks the split housing parts and that to Swan No. 534,021, issued Feb. 12, 1895, discloses essentially a one-piece pulley box housing.
None of these housing disclose an access cover plate. Access to these housings, as for instance to string a cable or a wire, requires entry through one of the conduits thereof.
Other known fittings of the type which do include cover plates for access to the housings, generally rely on threaded means to secure the cover plate; see for instance each of the U.S. patents to Church Nos. 1,681,097, issued Aug. 14, 1928, Scott 2,955,851, issued Oct. 11, 1960 and French Pat. No. 1,038,528. These devices obviously require threaded means incorporated in the housing structure and either threaded means on the cover plate or separate screw means. Further, these devices require an adequate work space for tool manipulation for access purposes.
Other fittings and covers of the type rely on interlocking beads, cleats or lugs to secure the cover plates; see the U.S. patents to Pate Nos. 4,073,514, issued Feb. 2, 1973 and Popp No. 2,665,353, issued Jan. 5, 1954. Such securing means require the fabrication of parts that increase costs.
The U.S. patent to Schaeffer No. 3,884,385, issued May 20, 1975, secures a cover plate on a fitting box of the type, by means of an extension on the cover plate that is forced to a locking position behind shoulder means formed in tab structure which extends from the box and thereafter permanently deforming said tabs to ensure fastening or in the case of resilient tabs, removing the cover plate only by the use of tool means.
Boynton et al, U.S. Pat. No. 1,669,447, issued May 15, 1928, in a fitting box of the type utilizes a channeled slide cover plate and a spring retaining means therewith. The combination of these parts of course results in increased costs and manipulative problems where space is limited.